This application is a 371 of PCT/EP96/00697 filed Feb. 20, 1996.
The invention relates to a sterile ophthalmic gel preparation that can be Applied in drop form, especially for use as an artificial tear fluid and for the treatment of xe2x80x9cdry eyexe2x80x9d, as well as to a method for the production of such a gel preparation.
It has been known for some time to use aqueous preparations to replace natural tear fluid and to treat xe2x80x9cdry eyexe2x80x9d, which aqueous preparations e.g. contain film-building materials based on polyvinylalcohol (PVOH), polyvinylpyrrolidone (PVP), cellulose derivatives or dextrane. An overview can e.g. be found in Sucker, Fuchs und Speiser, xe2x80x9cPharmazeutische Technologiexe2x80x9d 1978. These are generally systems which only have one fluid or liquid phase, typically an aqueous solution of further components.
Where components are present which are difficult to dissolve in water or which are water-insoluble, these are suspended as solids, in finally divided form, in the aqueous phase.
In semisynthetic preparations, such as e.g. those based on cellulose derivatives or dextrane, production is made more difficult by the fact that such materials are difficult to obtain free of insoluble components. One therefore has to incur very high expenditure in preparing solutions from such preparations which do not lead to eye irritation caused by mechanical effects. Further, such preparations are very difficult to sterilize, since they can only with great difficulty, or not at all, be filtered to remove germs, and they can also not be autoclaved without deteriation in quality. Cellulose derivatives cannot be autoclaved without irreversible changes in viscosity. Dextrane preparations are partly decomposed by autoclaving.
Also polyvinylalcohol can only be sterilized by heating if a very pure hydrolized form is employed since otherwise the PVOH component is depolymerized. Since PVOH as well as PVP only provide relatively little thickening effect, rather high amounts of these components must be used to provide suitable viscosities. This leads to a very high load of the ophthalmological preparation with such materials, e.g. contents of more than 10% in the case of PVOH.
It is already known from DE 34 40 352 and DE 43 03 818, and also from U.S. Pat. No. 5,252,318, to use polyacrylic acid and its derivatives, such as e.g. Carbopole(copyright) 940 (obtainable from B. F. Goodrich Company) as the gel basis for sterile ophthalmic gel drop preparations. In U.S. Pat. No. 5,441,732, which was only published after the priority date of the instant application, a combination of two specific gel components is disclosed, one of which is gelled thermally, whereas the other is gelled by a change in pH. Various cellulose derivatives are described as the thermally reactive gel polymer, whereas polyacrylates, especially cross-linked polyadrylates, are mentioned as polymers gelling in dependance of the pH value. It appears that gel formation is intended to only occur in the eye, by the pH change after application to the eye. It is stated that these-polymer mixtures are to be used together with organic oils, wherein a multiplicity of active agents can be dissolved. Vitamine A is not mentioned.
With respect to compliance, non-irritation, shelf life etc., very high-standards must be met by ophthalmic preparations which are to be used as film-forming preparations or lubricating preparations. Especially where ophthalmic preparations must be used for any extended period of time, which e.g. is regularly the case in the treatment of xe2x80x9cdry eyexe2x80x9d, even a temporary irritation, such as a burning sensation in the eye is an extremely unpleasant sensation, and is detrimental to any extended therapeutical treatment. It is self-understood that in the application of such ophthalmic preparations, impaired sight, blurred view or other acute irritations cannot be accepted.
In xe2x80x9cdry eyexe2x80x9d treatment, the use of vitamine A, generally in the form of vitamine A palmitate, has proven to be effective. Thus, gel drop preparations on Carbopol basis have been-commercialized (after the priority date of the instant application), which besides other customary components contain vitamine A palmitate. These are one-phase gels with a continuous aqueous liquid phase, and without any hydrophobic second liquid phase. These products have a shelf life of about a year, when the vitamine A component is provided in an excess of 40%. As trials have shown, the vitamine A content decreases by about 20% over six months in these preparations, so that at a 40% excess dosage, the guaranteed minimum content is still present after one year.
Natural tear fluid comprises inter alia a fatty component which comprises triglycerides and phospholipides. It has already been tried (WO 94/05298), to use triglycerides in synthetic tear liquids, which was, however, only possible when an emulgator was added, and the overall preparation was in the form of an emulsion, for topical application to the eye. This has the disadvantage that desirable residual amounts of natural tear fluid in the eye are destroyed by the emulgator component.
It is an important object of this invention-to provide ophthalmic preparations, especially gel preparations, which show an improved shelf life, especially when containing sensitive substances such as vitamine A and its derivatives.
It is a further important object of the invention to provide such preparations which do not cause acute irritations and impaired vision, especially when formulated for increased shelf life.
It is a further very important object of this invention to provide such preparations which make it possible to use the preparation repeatedly over an extended time period, and/or enable extended duration in the eye after each individual application without causing incompatibilities, lack of compliance, irritation to the eye and other such problems. The invention is based on various surprising findings.
On the one hand, it has surprisingly been found that relatively fast decomposition of vitamine A and its derivatives, especially vitamine A palmitate, in artificial tear fluids and preparations for xe2x80x9cdry eyexe2x80x9d treatment can be dramatically reduced when the preparation is in the form of a two component system with one aqueous liquid phase and one hydrophobic liquid phase. Especially it is preferred herein that the preparation-has a continuous aqueousphase wherein the hydrophobic liquid oil phase is provided in the form of very finely divided droplets. There is no easy explanation for this fact. Most probably, oxygen and/or light are responsible for the decomposition of vitamine A, and with respect to both, it should not make any material difference whether the preparation comprises one or two separate liquid phases. One would rather expect an increased, sensitivity with respect to oxygen and/or light in a solution of the vitamine A component in the hydrophobic phase.
Possibly, the simultaneous use of antioxidants, especially vitamine E and its derivatives and most specifically vitamine E acetate has an influence in these preparations. In any case, vitamine A is preferably used with such antioxidants in the inventive preparations.
On the other hand, a further surprising effect of the invention is that it makes it possible to prepare preparations with an aqueous and a liquid hydrophobic phase which come very close to the composition of natural tear liquid, and especially have a corresponding content of triglycerides, without any necessity of at the same time using emulgators. This is possible since according to the invention, such preparations are in the form of gel drop preparations. In contrast to preparations without any gel basis, triglycerides can be provided in the inventive gel preparations in the form of very finely divided droplets also over very extended storage periods, with the droplets being sufficiently stable in the gel even in the absence of any emulgator. It is possible without any problems to prepare such preparations so that they are sterile, and the preparations are not irritating and perfectly acceptable.
The inventive preparations, including gel preparations, have a refractive index which is almost completely the same as that of natural tear fluid. They provide extended duration and effect in the eye.
The inventive preparations appear to provide reduced surface tension of the aqueous eye gel, which leads to improved distribution on the cornea. Also, any active agent suspended or dissolved in the oil phase is more evenly distributed. wetability of objects to be placed on the cornea, such as contact lenses or the front: lenses of ophthalmological apparatuses, is improved.
Long term studies show that the inventive preparations are extremely stable in the 5 g polyfoil tube packages customary in trade, not only under the conditions of a temperate climate (29xc2x0 C., 45% relative humidity), but also under conditions of the mediterranian/subtropical climate (26xc2x0 C., 60% relative humidity) and even that of very hard and moist climates (31xc2x0 C., 70% relative humidity) and show hardly any changes in vitamine A content (where provided), pH value, osmolality, viscosity and appearance.
Basically, those ophthalmologically acceptable organic oils are suitable as the liquid hydrophobic component of the inventive two-phase preparations, especially gels, which can be dispersed as droplets in an aqueous phase in the absence of emulgators. Examples are formed by fatty acid derivatives such as, especially, fatty acid esters, triglycerides and phthalic acid esters. Triglycerides are presently specifically preferred, especially the homogeneous or mixed triglycerides formed,mostly or totally from C8-C12 fatty acids. Especially, medium chain triglycerides of the type defined in xe2x80x9cDeutsches Arzneibuchxe2x80x9d (DAB) 10 (1993) are preferred. The acid component of these triglycerides is a mixture of at least 95% n-octanoic acid and n-decanoic acid; the remainder is formed by shorter chain fatty acids.
Such medium chain triglycerides are made semi-synthetically from the oil of the dry solid part of the endosperm of cocos nucifera L., by hydrolizing the coco oil obtained from the endosperm, fractioning the thus obtained fatty acids, and re-esterification of the acids.
Such medium chain triglycerides are already in use as basic substances for cosmetics, as adjuvants and carriers for pharmaceuticals, and also for some foodstuffs. Very little is known, however, about their potential uses and the limits of such uses in ophthalmic preparations, although such medium chain triglycerides have very well known beneficial properties.
Inventive preparations, especially on gel basis, with typical contents between 0.1 and 3 weight-%, especially approximately 0.2 weight-% polyacrylic acid as the gel-forming agent in the aqueous phase, contain typically between 0.5 and 10 weight-%, especially approximately 1 weight-% of such medium chain triglycerides.
Inventive gel preparations preferably have a viscosity in the range of approximately 2000 to 6000 mPaxc2x7s, at a pH value between 6 and 8.
The inventive preparations preferably contain a preserving agent, such as especially centrimid, benzalkoniumchloride or thiomersal. It is further preferred that such gel preparations, contain at least one isotonic agent, for which purpose sorbitol is specifically suitable.
The especially preferred content of a vitamine A component, especially vitamine A palmitate, is of the order of 500 international units per gram of the inventive preparation. The vitamine A component is specifically preferred to be stabilized with a small amount of at least one antioxidant, wherein vitamins E and vitamine E acetate are specifically advantageous.
Production of an inventive sterile preparation, especially gel, proceeds in a multistep method. In preparing the gel, a sterile polyacrylic acid suspension is preferably obtained by the procedure disclosed in DE 43 03 818, i.e. by autoclaving at about 120xc2x0 C., 1 bar excess pressure, and 20 minutes duration. In parallel, an aqueous solution is prepared which contains the preserving agent and the isotonic, i.e. preferably centrimid and sorbitol. This aqueous solution is added to the autoclaved polyacrylic acid suspension by sterile filtration, using nitrogen as the pressurizing gas, or, in case, more simply using pressurized air. Subsequently, careful neutralization is achieved by adding sterile sodiumhydroxide solution, which initiates gel formation. Once neutralization has been achieved, there is no free base any more in the forming gel. The hydrophobic liquid component, i.e. preferably the medium chain triglyceride component, is then worked into the sterile gel under antiseptic conditions. Stirring is maintained until complete homogenization has been achieved. In the inventive dispersion, the size of the thus obtained oil droplets is maximally about 100 xcexcm and is otherwise of the kind, which is obtained in a conventional emulsion without the addition of strong emulgators.
The sterile gel can now be confectioned in the customary fashion.
Otherwise, an active agent such as especially vitamine A palmitate can be added to the thus formed sterile gel, in such a fashion that the vitamine A component and the much smaller amount of antioxidant, which is preferably also present, are dissolved in neutral oil, followed by sterile filtration. The sterile oil solution is then worked into the gel with stirring.
A comparable procedure is used when a preparation without gel basis, e.g. a drop solution is to be prepared.
The gel forming agents used according to this invention are preferably polyacrylic acids with a molecular weight of the order of approximately 3 to 5 million. Specifically preferred are the trade products such as Carbopol(copyright) polymeric acids as obtainable from B. F. Goodrich Chemicals Co. Carbopol 980 NF(copyright) is especially preferred. In the preparation, the concentration is approximately 0.2 weight-%.
The neutralization necessary for gel formation is customarily carried out using sterile diluted sodiumhydroxide solution, whereby 1-N sodiumhydroxide solution is specifically advantageous. However, also other inorganic bases or alkali carbonates, or organic bases such as amines, especially triethylamine and diisopropylamine can be used.
The gels thus obtained have viscosities in the range of approximately 2000 to 6000 mPaxc2x7s at 20xc2x0 C.
The preserving agent which is generally used according to this invention, such as centrimid, benzalkoniumchloride or thiomersal, is used in the customary concentration, i.e. approximately 0.01 weight-% in the case of centrimid. The isotoning agent, e.g. polyfunctional alcohols such as mannitol, dextrose, glycerol, propylene glycol or, especially preferred, sorbitol, are also used in customary concentrations. For sorbitol, a concentration of approximately 4.85 weight-% is specifically advantageous.